Kerala Nipah virus outbreak renews calls to protect bat roosts

It was more than two weeks before doctors even realised what they were treating, the fourth outbreak in five years of the lethal, brain-swelling Nipah virus in India’s Kerala region. By then, hundreds of people had been exposed to the bat pathogen.
Halting the disease’s spread required deploying an army of workers, who put this village and eight others on partial lockdown for two weeks, surveyed more than 53,000 houses for signs of illness and tracked down 1,200 people who had come into contact with infected patients, according to the World Health Organisation.
Ultimately, six people were infected, and two of them died. Though Kerala’s response to contain the outbreak drew international praise, the quick spread of the virus and its impact on tens of thousands of people illustrate what many scientists and world health leaders say is a weakness in public health policy: relying solely on disease containment. Governments, they say, must also control land development and protect animal habitats in areas where there is high risk of pathogens leaping from animals to people, a phenomenon known as spillover.
The lesson comes at an important time, as global health leaders work on a legally binding accord for responding to future global health crises. Though many have been advocating for spillover prevention measures, a main difficulty in the negotiations so far has been balancing the needs of emerging economies against the risk of unchecked development.
Because spillover risk is concentrated in lower income countries in the tropical south, the cost of preventing another pandemic falls squarely on nations that can least afford it.
Authorities in India’s national government say it’s a cost that can’t be ignored. Stopping bat viruses from spreading requires not just rapid response to outbreaks but careful monitoring of the bats themselves, said Subrat Mohapatra, a forestry official in India’s environment ministry. To that end, federal and state officials say they are talking about ways to protect bat habitats in areas where spillover risk is high.
“We have learned to manage the spillovers, but we have to constantly keep track of the high-risk zones as if they are volcanoes waiting to erupt,” Mohapatra said.
Analysis of environmental conditions and other factors that contribute to spillover makes it possible to identify danger zones so that governments can take steps to reduce risk. An analysis in May provided a roadmap of such areas.
Reporters compared ecological conditions across the globe from 2002 through 2020 with those that existed at the time of past spillovers, identifying 9mn sq km - covering 6% of the Earth’s land mass - where conditions were ripe for pathogens to jump from bats to humans. Nearly 1.8bn people lived in those jump zones in 2020, an increase of 57% since 2002.
The analysis focused on bats because they are linked to many of the deadliest disease outbreaks of the past half century, including the recent Covid-19 pandemic. Though its specific source is still unknown, the virus that causes Covid-19 is related to coronaviruses found in some horseshoe bats, a type common in tropical Asia. Kerala is one of the likeliest places on earth for spillover to occur, the analysis showed.
Bhupender Yadav, India’s minister of environment and forest, said talks are underway between his agency and state officials over the need to create “ecological protection zones” in areas at high risk of Nipah spillover.
Kerala Health Minister Veena George said the state government has created a new Nipah research centre in Kozhikode to investigate why spillover keeps occurring there and how to prevent it. Researchers will look at a wide range of factors, including tree loss, agricultural practices, urbanisation and community awareness - and what government actions are needed to reduce risk.
She cited protecting bat-roosting trees and planting native flowering trees - natural food for bats - as examples of what government could do.
A federal initiative to identify and protect ecologically sensitive areas in the region, begun more than a decade ago, stalled after encountering protests from landowners and resistance from state and local governments eager to boost their economies.
That same conflict is challenging global health leaders today as they work on an accord to govern response to future global health crises. The World Health Organisation’s 194 member states would be required under international law to adhere to the treaty. How they would be held accountable is among the issues still under debate.
The latest draft, released by the WHO on October 16, would require countries to conduct risk assessments for spillover as well as to “monitor and mitigate environmental factors associated with the risk of zoonotic disease spillover.” A growing body of research has linked deforestation, urbanisation and intensive farming to spillover.